Known camera technology, including cameras of the conventional film type, and digital cameras, consumer type cameras and professional type cameras, are based upon a usage model which requires a human photographer to point the camera at a field of view containing a subject of which a picture, image or video is to be captured, and activating a trigger button causing the camera to capture a still image, or in the case of a video camera, a moving picture scene.
Known still image cameras and video/film cameras for consumer and professional use are effectively products which are used by a photographer to capture an image or moving sequence of a scene, where the photographer consciously selects the scene, sets up the camera positioning for a particular view, and activates capture of an image or sequence of images as a photographer controlled activity.
In some cases, automatic triggers are provided on a timer device, whereby the photographer can set a camera up pointing at a scene, activate a time delay trigger, giving the photographer time to enter the scene, and then the camera automatically takes a picture or sequence once the pre-determined time limit has elapsed, allowing the photographer to appear in her own images.
There are also known prior art surveillance camera systems, which automatically capture still images or video sequences. Such cameras are used for security purposes in commercial premises such as factories and offices, as well as in domestic environments for security. These known cameras capture images or sequences of images in response to sensor activated events, such as an infra-red sensor being triggered, a movement sensor, or a circuit breaker sensor, for example a sensor which is activated when a door or window is opened. In general, this type of camera is wall mounted or mounted on posts, and pre-arranged to take a picture of a pre-determined scene. The cameras are not mobile and provide a permanent security monitoring installation.
In some cases, surveillance cameras are directable remotely from a central console unit, so that they can pan across a field of view and focus in and out of that field of view by remote control, the cameras being moved and controlled by servomotors.
There are also known surveillance cameras for other uses, for example traffic monitoring, and speed detection, which are triggered by motion sensors which detect vehicles moving within pre-set speed limits. This type of camera is conventionally installed in a permanent installation, pointing at a pre-determined scene.
The known surveillance cameras and traffic monitoring cameras are at fixed installations which operate without a human photographer, but are limited in their fields of view.
More recently, compact cameras have been installed in personal communication devices, such as mobile phones. Pictures of individuals can be taken using hand held devices, and sent as messages over a wireless communication network to personal handsets of other users. With these hand held devices, the basic mode of usage requires a person to act as a photographer, pointing the device at a field of view, for example directing the device at their own face to take a picture of themselves, and activating capture of an image by triggering a switch.
The concept of a user wearable camera device receiving attention clues from a host wearer and capturing images is known. For example in Summarizing Wearable Video, K. Aizawa, K. Ishijima, M. Shiina, IEEE, International conference on image processing, III:398-401, Thessaloniki, Greece, 2001, there is disclosed a system which receives sensor inputs from a host wearer, and which attempts to understand those sensor inputs in order to determine when to capture an image.
Other known works which analyze a host wearer's attention from a self perspective point of view include the following:                J. Healey and R. W. Picard, “StartleCam: A Cybernetic Wearable Camera”, In Proceedings of the International Symposium on Wearable Computers, pages 42-49, 1998;        A. Lockerd, F. Mueller, “LAFcam—Leveraging Affective Feedback Camcorder”, ACM CHI, 2002; and        Y. Nakamura, J.Ohde, Y. Otha, “Structuring personal activity records based on attention: Analysing vidoes from a head-mounted camera”, in International Conference Pattern Recognition, Barcelona, September 2000.        
Known usage models and systems for detecting a person's attention focus on analyzing the actions and behavior of the person from the perspective of that person, that is, analyzing parameters which are local to the person and in the immediate vicinity of the person.
A further body of work concerned with observing a person from a position external of that person, that is from an external perspective includes the following items:                A. Pentland, “Looking at People: Sensing for Ubiquitous and Wearable Computing, IEEE Trans. Pattern Analysis and Machine Intelligence, IEEE CS Press, Los Alamitos, Calif., January 2000, pp.107-118;        M. Trivedi, I. Mikic, S. Bhonsle, “Active Camera Networks and Sematic Event Databases for Intelligent Environments”, IEEE Workshop on Human Modeling, Analysis and Synthesis, June 2000;        A. Pentland, T. Choudhury. “Face Recognition for Smart Environments”,IEEE Computer, vol. 33, no. 2, February 2000, pp. 50-55;        D. Gavrila, “The Visual Analysis of Human Movement: A Survey”, Computer Vision and Image Understanding, vol. 73, no.1, January 1999, pp. 82-98;        V. Pavlovic, R. Sharma, T. Huang, “Visual Interpretation of Hand Gestures for Human-Computer Interaction: A Review”. IEEE Trans. PAMI, vol. 19, no. 7, July 1997, pp. 677-695;        R. Stiefelhagen, J. Yang, A. Waibel, “Estimating focus of attention based on gaze and sound”, Proceedings of the Workshop on Perceptive User Interfaces, 2001; and        R. Vertegaal, R. Slagter, G. van der Veer, A. Nijholt, “Why conversational agents should catch the eye”, In Summary of ACM CHI Conference on Human Factors in Computing, The Hague, 2000.        
Some known devices such as disclosed in the above bodies of work could be referred to as ‘s’, which observe a person from a position external of that person.